wave-roll
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JavaScript Library for Comparative MIDI Piano-Roll Visualization
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Markdown
# WaveRoll
<div style="text-align: center;">
<img src="./wave-roll-logo.png" alt="WaveRoll" width="40%"/>
</div>
> **WaveRoll** is an interactive [JavaScript library](https://www.npmjs.com/package/wave-roll) that enables comparative visualization and synchronized playback of multiple MIDI piano rolls on a browser.
[](https://arxiv.org/abs/2511.09562)
- You can try the web demo at [https://crescent-stdio.github.io/wave-roll/](https://crescent-stdio.github.io/wave-roll/).
- NPM package: [https://www.npmjs.com/package/wave-roll](https://www.npmjs.com/package/wave-roll)
- VS Code Extension: [WaveRoll Studio](https://github.com/crescent-stdio/wave-roll-studio) (also available on Open VSX)
- Multi-instrument MIDI files are supported with automatic GM instrument mapping and per-track mute/volume/visibility controls.
## Installation
### [NPM: wave-roll](https://www.npmjs.com/package/wave-roll)
```bash
npm install wave-roll
```
### Usage (NPM)
```html
<!DOCTYPE html>
<html>
<head>
<script type="module">
import 'wave-roll';
</script>
</head>
<body>
<wave-roll
style="width: 100%;"
files='[
{"path": "./audio/track.wav", "name": "Track Audio", "type": "audio"},
{"path": "./midi/ground_truth.mid", "name": "Ground Truth", "type": "midi"},
{"path": "./midi/modelA.mid", "name": "Model A", "type": "midi"}
]'>
</wave-roll>
</body>
</html>
```
### Using CDN (ES Module)
You can try the ES Module demo [here](https://crescent-stdio.github.io/wave-roll/examples/es-module/) and [sample codes](https://github.com/crescent-stdio/wave-roll/blob/main/docs/examples/es-module/index.html).
```html
<!DOCTYPE html>
<html>
<head>
<script type="module">
import 'https://cdn.jsdelivr.net/npm/wave-roll@latest/dist/wave-roll.es.js';
</script>
</head>
<body>
<wave-roll
style="width: 100%;"
files='[
{"path": "./audio/track.wav", "name": "Track Audio", "type": "audio"},
{"path": "./midi/ground_truth.mid", "name": "Ground Truth", "type": "midi"},
{"path": "./midi/modelA.mid", "name": "Model A", "type": "midi"}
]'>
</wave-roll>
</body>
</html>
```
### Using UMD CDN (Traditional Script)
You can try the UMD demo [here](https://crescent-stdio.github.io/wave-roll/examples/umd/) and [sample codes](https://github.com/crescent-stdio/wave-roll/blob/main/docs/examples/umd/index.html).
```html
<!DOCTYPE html>
<html>
<head>
<script src="https://cdn.jsdelivr.net/npm/wave-roll@latest/dist/wave-roll.umd.js"></script>
</head>
<body>
<wave-roll
style="width: 100%;"
files='[
{"path": "./audio/track.wav", "name": "Track Audio", "type": "audio"},
{"path": "./midi/ground_truth.mid", "name": "Ground Truth", "type": "midi"},
{"path": "./midi/modelA.mid", "name": "Model A", "type": "midi"}
]'>
</wave-roll>
</body>
</html>
```
### GitHub Pages Usage
For GitHub Pages deployment, you can use the CDN directly:
```html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>WaveRoll Demo</title>
<script type="module">
import 'https://cdn.jsdelivr.net/npm/wave-roll@latest/dist/wave-roll.es.js';
</script>
</head>
<body>
<wave-roll
style="width: 100%"
files='[
{"path": "./audio/track.wav", "name": "Track Audio", "type": "audio"},
{"path": "./midi/ground_truth.mid", "name": "Ground Truth", "type": "midi"},
{"path": "./midi/modelA.mid", "name": "Model A", "type": "midi"}
]'>
</wave-roll>
</body>
</html>
```
### In React
```jsx
import 'wave-roll';
function MidiComparison() {
const files = [
{ path: "./audio/track.wav", name: "Track Audio", type: "audio" },
{ path: "./midi/ground_truth.mid", name: "Ground Truth", type: "midi" },
{ path: "./midi/modelA.mid", name: "Model A", type: "midi" }
];
return (
<wave-roll
style={{ width: '100%' }}
files={JSON.stringify(files)}
/>
);
}
```
### Standalone Demo
Try the standalone version with drag-and-drop file upload interface:
- **Live Demo**: [https://crescent-stdio.github.io/wave-roll/standalone.html](https://crescent-stdio.github.io/wave-roll/standalone.html)
- **Source Code**: [docs/examples/standalone.html](https://github.com/crescent-stdio/wave-roll/blob/main/docs/examples/standalone.html)
The standalone demo is a minimal, ready-to-use interface where users can directly upload and compare MIDI/audio files without any additional setup.
### Using in Jupyter Notebook
You can embed WaveRoll in Jupyter notebooks using `IFrame`:
```python
from IPython.display import IFrame
IFrame(src='https://crescent-stdio.github.io/wave-roll/standalone.html', width='100%', height='800px')
```
- **Example Notebook**: [docs/examples/jupyter-notebook/wave-roll-demo.ipynb](https://github.com/crescent-stdio/wave-roll/blob/main/docs/examples/jupyter-notebook/wave-roll-demo.ipynb)
- **Open in Google Colab**: [](https://colab.research.google.com/github/crescent-stdio/wave-roll/blob/main/docs/examples/jupyter-notebook/wave-roll-demo.ipynb)
This is particularly useful for music information retrieval (MIR) research, allowing you to visualize and compare transcription results directly in your analysis notebooks.
## API
### Attributes
| Attribute | Type | Description |
|-----------|------|-------------|
| `files` | `string` | JSON string array of file objects with `path` and `name` properties |
| `style` | `string` | CSS styles for the component container |
| `readonly` | `boolean attribute` | When present, hides UI controls for adding/removing files (read‑only mode) |
#### Read‑only Mode
Add the `readonly` attribute to disable file addition and deletion in the Settings modal (the "Add MIDI Files" button and per‑file delete buttons are hidden):
```html
<wave-roll
style="width: 100%; height: 600px;"
files='[
{"path": "./audio/track.wav", "name": "Track Audio", "type": "audio"},
{"path": "./midi/ground_truth.mid", "name": "Ground Truth", "type": "midi"},
{"path": "./midi/modelA.mid", "name": "Model A", "type": "midi"}
]'
readonly
></wave-roll>
```
You can toggle this at runtime too:
```js
const el = document.querySelector('wave-roll');
el.setAttribute('readonly', ''); // enable read-only
el.removeAttribute('readonly'); // disable read-only
```
### File Object Structure
```typescript
interface FileItem {
path: string; // URL or relative path to the file
name: string; // Display name shown in UI
type?: "midi" | "audio"; // Defaults to "midi" when omitted
color?: string; // Custom color for track visualization (hex or CSS color)
}
```
### JavaScript API
Control the player programmatically:
```javascript
const waveRoll = document.querySelector('wave-roll');
// Playback controls
await waveRoll.play();
waveRoll.pause();
waveRoll.seek(30); // Seek to 30 seconds
// State
console.log(waveRoll.isPlaying); // boolean
console.log(waveRoll.getState()); // { currentTime, duration, tempo, ... }
```
### Tempo Control
WaveRoll includes an interactive tempo control with popover input:
- Click the BPM badge in the player controls to adjust tempo
- Supports a wide range of tempo adjustments
- Audio playback automatically adjusts with pitch preservation
### MIDI Export
Export MIDI files with modified tempo via the Settings panel:
1. Adjust tempo using the tempo control
2. Open Settings (gear icon)
3. Click "Export with Current Tempo"
The exported file preserves all note data with updated tempo metadata.
**Programmatic usage:**
```javascript
import { exportMidiWithTempo } from 'wave-roll';
// Export MIDI with new tempo (triggers download)
await exportMidiWithTempo(midiFile, 144);
// Export as Blob for custom handling
import { exportMidiWithTempoAsBlob } from 'wave-roll';
const blob = await exportMidiWithTempoAsBlob(midiFile, 144);
```
## Development
```bash
# Install dependencies
pnpm install
# Run development server
pnpm dev
# Build for production
pnpm build
# Run tests
pnpm test
```
## Acknowledgments
This library includes functionality ported from [mir_eval](https://github.com/mir-evaluation/mir_eval), Music Information Retrieval evaluation library.
## License
MIT License - see [LICENSE](LICENSE) file for details
## Citation
If you use WaveRoll in your research, please cite:
```bibtex
{waveroll2025,
title={WaveRoll: JavaScript Library for Comparative MIDI Piano-Roll Visualization},
author={Park, Hannah and Jeong, Dasaem},
booktitle={Proceedings of 26th International Society for Music Information Retrieval Conference (ISMIR)},
year={2025}
}
```